Perkin Rearrangement (Coumarin-Benzofuran Ring Contraction)

W. H. Perkin, J. Chem. Soc. 23, 368 (1870).

Formation of benzofuran-2-carboxylic acids and benzofurans by heating 3-halocoumarins with alkali:

R. C. Elderfield, V. B. Meyer, Heterocyclic Compounds 2, 2, 5 (1951); K. Bowden, S. Battah, J. Chem. Soc. Perkin Trans. II 1998, 1604.